The present invention relates to an improved fuel injection nozzle which is adapted to reduce combustion noise in an internal combustion engine during cranking and idle speed operation.
The type of fuel injection nozzle to which the present invention constitutes a novel improvement is provided for each cylinder of an internal combustion engine such as a Diesel engine. A fuel injection or metering pump of the distribution type feeds fuel to the injection nozzle at the correct timing in the engine operating cycle and in the correct amount. This type of injection nozzle generally comprises a spring-loaded valve which is normally closed and is opened when the fuel pressure from the pump exceeds a predetermined value to discharge fuel from an injection or discharge orifice of the nozzle into the engine cylinder.
A problem has existed in the art thus far in that fuel injection is excessively fast under low speed operating conditions such as cranking and idling. This results in overly rapid combustion and excessive combustion noise.
U.S. Pat. No. 3,559,892 to De Luca discloses a fuel injection nozzle of the present general type and means for improving combustion at low speed. Said means comprise an auxiliary fuel discharge orifice of small diameter which is uncovered for fuel injection when the fuel pressure is above a first predetermined value and a main fuel injection orifice of larger diameter which is also uncovered when the fuel pressure is above a second predetermined value which is higher than the first predetermined value. Whereas De Luca's disclosure constitutes a valuable contribution to the art, it is particularly directed to engines in which fuel is sprayed on the piston cavity wall and is difficult to incorporate into other types of engines.